1. Field of the Invention
The present invention relates to an image reading apparatus, and particularly relates to a flatbed image reading apparatus.
2. Description of the Related Art
One of conventional image reading apparatuses applied to an image scanner, a photocopier, a facsimile, a character recognition device, and the like, is a flatbed (FB) image reading apparatus that reads image data of a medium, for example, a book or a magazine, by arranging the medium on a platen and moving a line image sensor over the medium. Because the medium is arranged on the platen for reading its image data, the flatbed image reading apparatus can read a relatively thick medium, such as a book or a magazine. When using such flatbed image reading apparatus, a medium is sometimes left behind on the platen in some cases after image data of the medium arranged on the platen is read, for example, due to carelessness of a user. To avoid leaving behind a medium, an image reading apparatus is provided with a hardware device such as an additional sensor at a point where the medium is to be arranged, and configured to determine that the medium is removed by detecting the presence or absence of the medium with the additional sensor after predefined processing is finished, and by detecting a movement of opening and closing of a lid or other parts that covers the medium while reading image data.
Alternatively, for example, an image reading apparatus disclosed in Japanese Patent Application Laid-Open No. 2005-72947 is an image reading apparatus configured to avoid leaving behind a medium on the platen as well as to suppress increase in the number of parts, such as addition of the sensor, which may otherwise result in an increase in production cost. The image reading apparatus includes an original holder (or a lid) that covers and uncovers a transparent board (or a platen) on which an original is to be laid, and an inside surface of the original holder is configured as a fixing unit that is luminous by storing therein light and emitting light by itself. After reading operation of an original is finished and then a certain time passes over, as a solid-state imaging device receives light emitted from the fixing unit when an open-close detecting unit detects a closed state of the original holder, the image reading apparatus detects the presence or absence of a left-behind original based on the amount of light received by the solid-state imaging device while the original holder is still closed. A medium-remainder detecting device of an image scanner disclosed in Japanese Patent Application Laid-Open No. 2001-223840 is configured to detect the presence or absence of a remaining medium on a reading-medium arrangement surface by reading image in a state that nothing is laid on the reading-medium arrangement surface and storing therein compressed data of read image data, then re-reading the medium after finishing predefined processing and compressing the re-read image data, and comparing a file size of the compressed re-read image with a compressed file size of the image when nothing is laid.
However, the image reading apparatus disclosed in the patent document No. 2005-72947 needs to detect the presence or absence of a left-behind original in a closed state of the original holder that covers and uncovers the transparent board, therefore, the technology cannot be applied to an image reading apparatus that does not include the original holder. The medium-remainder detecting device of an image scanner disclosed in the patent document No. 2001-223840 needs to read image data of the whole of a medium as a reading subject only for detecting the presence or absence of a left-behind original, so that the amount of processing data may be increased.